httpserver: fix JSON boolean formatting

The JSON standard specifies that boolean values should be written
as 'true' and 'false' (without the quotes). The standard goes as
far as specifying the ASCII values of these letters, and in particular
it is case sensitive - one cannot write True or TRUE as a synonym of true.

We erronenously used True/False with a capital letters. Python's
JSON parser, for example, fails to recognize such broken JSON.
So this patch fixes this.

Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Reviewed-by: Tomasz Grabiec <tgrabiec@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
Revert "trace.py: optimize unpack()"

This reverts commit c077d1fd8efbc007e137262962c8a504bd269eee.

The change breaks 'trace extract':

[penberg@localhost osv]$ trace extract
warning: Unable to find dynamic linker breakpoint function.
GDB will be unable to debug shared library initializers
and track explicitly loaded dynamic code.
sched::cpu::do_idle (this=this@entry=0xffff80000113a040) at
/home/penberg/osv/core/sched.cc:388
388             handle_incoming_wakeups();
Python Exception <type 'exceptions.TypeError'> unpack_from() argument
1 must be convertible to a buffer, not concat:
Saving traces to tracefile ...
Error occurred in Python command: unpack_from() argument 1 must be
convertible to a buffer, not concat

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>